Metal working



March 5, 1957 J. KARMAZIN, sR 2,783,726

METAL WORKING 2 Sheets-Sheet l Filed April 27. 1953 INVENTOR March 5, 1957 J. KARMAzlN, SR 2,783,726

METAL WORKING Filed April 27, 195s 2 sheets-sheet 2 F'G- nl t' 20 W if mvENToR METAL WORKING John Karmazin, Sr., Grosselle, fMich.

Application April 27, 1953,. Serial `No."351;279

3 Claims'. .v (Cl..-l=13f38) This invention relates to metalworking and .more parnticril'arly 'to a machine for'use in manufacturing Aheat `exfchangers of the lin and tube typejwherein'astack of super- -posed iin elements having 'integral` tapered` tubular profjections are arranged in telescopic relationship.

'It-isa'n object of this invention to providea 'die v.for manufacturing heat exchangers in which -a strip of sheet metal is progressively reformed Ato provide rows `o'f'tubular portions withoutthinning or weakening the material form- `ingthetubular portions beyond the ldesired 'strength 're lquiren'rents Yj The' inventionV represents an improvement "over the method and machine shown in myV priorjPatent No. "1Q-669,761.

One of thebig problems in manufacturing Qheat exchangers ofthe type disclosed hereinis thatY of forming 'the tapered tubular projections onjthe iin' elements s o as Anottonrrdulyweaken the metal in they tubul'arprojections. Iir'r'nachines of the type -previously'used the'successive dies which were used lin forming the tubular' projections 'had their sidev wallsY yarranged at progressively vsteeper angles. This has been :clearlyillustrated in Figure 7 in 'my'vUnited-States Letters Patent No.*1,^669',7'61.^ The vuse -of-progressively'steeper dies results'in rapid deteriora- -tion of-the dies. Some of the larger manufacturers of heat exchange units 'have found it necessary to discontinue the -nse -of tubular projections struckeout from apiece of sheet metal, for the reason that the tooling ucostsjrn'ade 'the-cost of the-heatexchang`e vunits tooihigh, as compared with the cost of pipes projectedthrough-aperturesdissheet metal tins. By arranging the dies lat progressively increas ing angles,- lany variation` in the' `thickness o'ffthe sheet metal resultsjinsome of -the dies near none-end of the die lassembly absorbing practically all of the impact ofthe `punch'pressiand the other dies absoibingfpractirally' none. If,for'example, the thickness of thestock metal .is'increased; the `dies at 'one end of the gang of dies absorbs practically all of the impact. On the other hand, if the thickness of the metal is decreased, the dies in the opposite end absorb practically all of the impact. The dies receiving the greatest impact fail, resulting in the necessity of replacing portions of the dies, realigning these replaced portions, et cetera. Moreover, the stock is overstressed, weakened and frequently ruptured by the overloaded dies.

It is thus a further object of this invention to provide a progressive die on which a succession of sets of tapered male and female die members have a uniform taper angle, whereby impact forces of the series are more uniformly distributed over the individual die sets, with changes in thickness of stock being worked upon, whereby wear on the individual sets is reduced, and the stock is not ruptured or weakened in the forming process.

Other objects and advantages reside in the construction of parts, the combination thereof and the mode of operation, 'as will become more apparent from the following description.

In the drawing:

United States PatentO i facture into vla lheat exchanger. As thefstripml 2,783,726 .Patented Mar.,i `E, i195?? 2 Figurel is aplanview showing "a pl'talityf fl'ifjystrips in the process of; manufacture;

Fguel `AiS "a 'Sectionl Yev'kel' libsfailiiuy "3.19112 "thefcentr line ofne of. the` fxrstr'iil4 `Sh`f0wn ,'F elite 1;

Figure `3` isy a vertical sectional view how gf eponstruction 'and arrangement of fthe Successiyegdies'ised 'in forming tubular projections on' thenstrips; n

Figure 4 is a plan'viewshowingj a'j'pafir 1v of tir'1` s`tri pfs1hav ing circular tubular. projections iny theprocess of 'manufacture; and v :Figure 5 is a fragmentary 4elevational]'vieu/sh section of heat exchanger vmanufacture in acc with my invention. y

Referring now tothe '-drawingjreference "initnerall '10 gdesignatesY a` thin` sheet lrnetal'hstrip in' the .process .tif u- .Passes through .thep'unch press, it is slitor precut into t or more strips as indicated'by the parallel 'lines' 1,2,js;o s to -formga plurality of nstrips '14 having'integral'ly'formed `tubular projections 16. t 'l n Y For -purposes of illustratingthe invention,` "there" is lshown -in-Figure 3 of the drawingone set ofs'uccessive dies which is `used `inl progressively forrnirrg'j the 4irijtegral Aprojections on a single `iin-strip, ',whereas there aresix 'se'ts of these 'dies arranged, si'de'byside s o as vto make it possible to form six 'separate finA strips, vif desired,"or to form six rows of tubular projectionsv on a *single fin ,strip. For'purposes of illustra-ting the invention', there has'been shown in Figure "l of thedrawing an"arrangementin'which 'la sing-le dwide strip ofgsheet metal-isjslit into siX narrower stripsfwherea's certain aspects of the 'invention areequally Y applicableto an arrangementy in lwhich `alessernumber of hrslits are @made in the' strip. Thus, one i'could, for example, yslitthestrip'so as to A form three `double row Ifir'rltube sections or 'onecould -so` slit the strip as'to1form`one four rowftin `stripefanclone-two row fin strip 'or 'any other ''ombinationof-numbers.- vVthere'as Figuresl-and'show an `arrangerrient in vvwhichgthe tubular-projections are'v sodesigned-as'to form-ttube`shaving an oblong opening-so that the v-`tubes are relatively flat, Figure 4 lshows, `an y'arrangement in which circular tubes would be-fornedj. *Rather than duplicating theshow'ing of'` dies Lfor bothtype's of tube ft'vrmations,` therefhas-.beeii -shown ih'igurey lfthe `'one -set of-fdi'es -fo`r` "use fir'r `making the jibundftubes. he -sa'mei principles are -applicable for 'making V` `the round lsha'pedtubes vas for making the `iiatter tubes. n *JThese-tubularprojections 16 `are Y'for'nreti in ',a punch press'ofetheageneral type shown Yin Figure `3 `wlrelre'ir'ian 'itipperdie member v18 mounted ona conventional plunger 20'moves `ve"rtically-fwith respect to the lower `4dieho'lder 22m-'The sheetmetal strips;v such asstrip 10,*arefi`ed in betweenthe dies --andare 'advanced'rfrom 'left to"`right. A plate or die holder 24 is drilled to receive and support the forming tools or male dies 26. The lower die member 22 is provided with complementary recessed female dies 28 which are arranged in alignment with the forming tools or dies 26. Spring pressed plungers 30 are arranged as shown and are adapted to lift the strip being formed out of the die recess to permit the strip to be fed forward. An intermediate stripper plate 32 which is perforated to permit sliding movement of the forming tools 26 is provided as shown and serves as a stripper. The plate 32 is in effect a tiat faced plunger or pressure pad which is adapted to cooperate with the lat top of the lower die member `22 to flatten or smooth out the metal strip passing through the forming die. The function of the various dies 26 is to progressively form on and from the strip 10 rows of integral tubular projections transverse to the strip and to accomplish this result without rupturing the strip or materially lthinning or weaken` ing the metal beyond the requisite requirements which goes into the tubes. To this end `the first-fof the dies 26 which the( strip encounters is adapted to form broad rprojection or bulge on the under side thereof, such as the depression 40.

The second of the dies 26 which is encountered by the strip serves to partially reduce and draw in the sides of the strip so as to reduce the width of the strip, as clearly indicated in Figures 1 and 4. The succeeding dies 26 progressively deepen and narrow the depressions or tubular projections 16 as shown in Figures l and 4. Each succeeding operation progressively reduces the diameter or the length of the transverse periphery.

The rst tool and die 26 cooperate to form a recess on one side of the sheet metal and a bulge on the opposite side. The cross sectional area of this recess, taken in the plane of the sheet metal, is much larger than a cross sectional area taken in the plane of the sheet metal of the ultimate tubular projection. The tools or dies 25 and 28 decrease in transverse cross sectional area progressively, so that each succeeding set of dies is smaller in transverse cross sectional area than the cross sectional area of the preceding set of dies. T he length of each succeeding die 26 and the depth of the succeeding die 28 increases, so that the metal of the bulge is gradually t reduced in cross sectional area and at the same time gradually elongated. Substantially all of the metal found in the final tubular projection has been derived from the metal inthe first bulge that is formed.

In the nal operation in forming the tubular projections, the bottom of the cavity is punched out or severed, so as to open up the bottom of the recess or cavity. The side walls of the frustum-conical portions of the recess bear a constant angle with respect to the plane of the sheet metal from thebeginning to the next to the last forming operation. In other words the elements generating the successive rustum-conical projections `form the same angle with the plane of the sheet metal strip throughout each of the forming stages with possibly the exception of the last forming operation. During the last forming operation, the angle may be changed slightly, so as to properly telescope the tubular projection of one member into the tubular projection of an adjoining member of the heat exchange unit.

One of the big distinctions between dies of the type shown in Figure 3 of the drawing and the type formerly used and shown in my prior Patent No. 1,669,761 is that the sides of the dies 26 and 28 are all arranged at the same angle which preferably is a 5 angle. The angle may be a little more or a little less than 5? providing the angle of all the dies is the same with the possible exception of the last one. By virtue of providing progressive dies 26 and 28 in which the sides of the main forming dies have a 5 angle, the wear on the dies will alect all dies in the same manner and consequently it will not be necessary to provide shims as the dies Wear. The last of the dies 26 to encounter the strip may have an angle slightly less than the 5 angle so as to accurately shape the tubular projection so that the telescoping tube sections will telescope the proper distance and provide a tight joint.

Frustum-conical, as used herein, is used to designate side Walls of the recesses and the bulges or projections as shown in Figure l or as shown in Figure 4. In other words, the conical section need not necessarily have a round base. It may have an oblong or elongated base, as shown in Figure l.

Tubular projections, as used herein, is used to designate the projections made according to this invention, whether they are round, oblong or some other configuration.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changesV may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode 'of operation, which generally stated consist in a device capable `'of carrying out the objects set forth, as disclosed and dened in the appended claims.

Having thus described my invention, I claim:

l. A" progressive die for drawing tapered tubular projections from a sheet of material, said die including a progressive series of aligned sets of male and female die members, the male die members being mounted on a common die holder so as to be moved in unison relative to the female die members, each of the male and female die members being of conical form and having the same angle of taper, whereby the impact forcerof the series is more evenly distributed over the individual die sets with changes in thickness of the sheet material, each succeeding s et of dieshaving a reduced crossV sectional area with the same taper and each succeeding set of dies yhaving longer male and female die members than preceding sets, so as to progressively reduce the diameter of the projections and increase the length thereof without changing the angle of the side walls of the projections.

2. The structure of claim l wherein an initial die set serves to draw a bulge directly from said sheet and wherein one or more finishing die sets follow said uniformly tapered die sets.

3. The structure of claiml wherein said angle of taper is substantially five degrees (5).

References Cited in the le of this patent UNITED STATES PATENTS 1,669,761 Karmann May 15, 192s 2,260,891 Ekstedt et al Oct. 28, 1-94l 2,656,808 Plumeri er a1 oct. 27, 1953 

